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Javascript Form Validate Empty Field function

Article by:  Jeff Anderson  ( 1361 ) (2/26/2002)
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Summary: This javascript function allows you to check whether a form field has been completed or not.
Viewed: 141213 times Rating (34 votes): 
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This function can be used to check whether the user has entered anything in a given field. There are two possibile types of 'emptiness' a form can return - a zero length string, or a null value. Here we simply check both these options, and return true if either of these are found to be true.




function IsEmpty(aTextField) {
   if ((aTextField.value.length==0) ||
   (aTextField.value==null)) {
      return true;
   }
   else { return false; }
}	


To check the particular field, you need to pass it in, in the form document.formname.fieldname

It's important to remember to give your form a name in the <form> tag which is referenced here. So, for example, if your form name is form1, and the field name is 'address1' you call the IsEmpty function as follows :


To understand more about how to use the IsEmpty function to validate a form, see Form Validation function






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User Comments on 'Javascript Form Validate Empty Field function'
Posted by :  Archive Import (Zoya) at 02:15 on Monday, September 09, 2002
This function will interpret a string of spaces as a filled out field, although it is considered empty in most practical cases. Also, value of a text field is never Null, but rather a zero-length string. I think this code would work better:
function isEmpty(aTextField){
var re = /s/g; //Match any white space including space, tab, form-feed, etc.
var str = aTextField.replace(re, "");
if (str.length == 0) {
return true;
} else {return false;}
}
Posted by :  Archive Import (Zoya) at 03:22 on Monday, September 09, 2002
Correction for the previous post:
function isEmpty(aTextField){
var re = /\s/g; //Match any white space including space, tab, form-feed, etc.
var str = aTextField.replace(re, "");
if (str.length == 0) {
return true;
} else {return false;}
}
Posted by :  Archive Import (Ghassan Beydoun) at 06:03 on Tuesday, October 15, 2002
Correction for the previous post (IE support):
function isEmpty(aTextField){
var re = /\s/g; //Match any white space including space, tab, form-feed, etc.
RegExp.multiline = true; // IE support
var str = aTextField.replace(re, "");
if (str.length == 0) {
return true;
} else {return false;}
}
Posted by :  Archive Import (Kay) at 18:31 on Saturday, November 09, 2002
The following code didn't work for me:

function isEmpty(aTextField){
var re = /\s/g; //Match any white space including space, tab, form-feed, etc.
RegExp.multiline = true; // IE support
var str = aTextField.replace(re, "");
if (str.length == 0) {
return true;
} else {return false;}
}

I received a message that the property or method wasn't supported on the following line:

var str = aTextField.replace(re, "");

Does anyone have any ideas or have they gotten this code to work?

I was able to the following code to work but it allows spaces as being true and that won't work for what I need.

Thanks in advance,

Kay
Posted by :  Archive Import (Kay) at 18:33 on Saturday, November 09, 2002
Sorry. I forgot to add the code that did work. Here it is:

function IsEmpty(aTextField) {
if ((aTextField.value.length==0) ||
(aTextField.value==null)) {
return true;
}
else { return false; }
}

Thanks,

Kay
Posted by :  Archive Import ( ) at 13:09 on Thursday, November 21, 2002
Posted by :  Archive Import (djanes) at 08:52 on Saturday, November 23, 2002
this is sweet
Posted by :  Archive Import ( ) at 18:02 on Monday, December 09, 2002
Posted by :  Archive Import (waleed wahba) at 07:59 on Wednesday, December 11, 2002
if(document.form.text1.value=="")
{
alert("Invaled");
return false;
}
Posted by :  Archive Import (1) at 11:27 on Wednesday, January 22, 2003
no
Posted by :  Archive Import (Terry) at 22:44 on Wednesday, June 11, 2003
I came across this code and I am novice at javascript. Is there a way to determine if the form field has not been completed. Then, automatically input a default value for the non-completed form field? Then, it will process based on default values. Thanks for any ideas.

Terry
Posted by :  Archive Import (Abe) at 08:14 on Friday, June 13, 2003
There is a way to set default values. If the field is not completed set document.nameofform.nameoffield.value to whatever you want the field to be.
Obviously, you'll need to replace "nameofform" and "nameoffield" to whatever their names are in your HTML code.
Posted by :  Archive Import (dude) at 17:02 on Sunday, July 20, 2003
To Zoya,

Your Code works perfect! It is a good code for checking Empty and any white spaces in the form fields.

Thank you for that!

Regards,
a dude
Posted by :  Archive Import (Judy) at 19:09 on Tuesday, August 05, 2003
Will this function work in reverse? I have 4 text fields and require only one to be completed. Only if a field is completed should it then be validated. I have tried the following with no success in IE. The first part works, but the second part it ignored.

function validate(){
if ((document.housecall.email.value == "") && (document.housecall.phone.value == "") && (document.housecall.cell.value == "") && (document.housecall.pager.value == ""))
{
alert('Please provide your contact information');
return false;
}
else if ((document.housecall.email.value.length!=0) || (document.housecall.email.value!=null) || (document.housecall.email.value!= ""))
{
alert('Validate email');
return false;
}
}
Posted by :  Archive Import (Rockett_Drummer) at 18:21 on Friday, August 08, 2003
What tag does the code go next too? Does it go in the tag or next to it?
Posted by :  Archive Import (Judy) at 16:40 on Saturday, August 09, 2003
I'm not sure what you mean. Perhaps viewing the whole page will help...

http://www.glass-dr.com/form_test.htm
Posted by :  Archive Import (Jr k kurien ) at 02:33 on Wednesday, September 10, 2003
I would like to have a validation code for trimming white spaces in the beginning as well as ending of a string.
Posted by :  Archive Import (Jr k kurien ) at 02:37 on Wednesday, September 10, 2003
I would like to have a validation code for trimming white spaces in the beginning as well as ending of a string.Expecting a quick response.
Posted by :  bethchebaygolly at 22:59 on Sunday, December 12, 2004
I got a problem with trimming my string...i have a field which requires an input. when the user tries to input a space it still updates the data. what will i do?
Posted by :  xman at 18:41 on Thursday, June 09, 2005
Actually, here is a better function without any workarounds for crappy browsers like IE:

function isEmpty(mytext) {
var re = /^\s{1,}$/g; //match any white space including space, tab, form-feed, etc.
if ((mytext.value.length==0) || (mytext.value==null) || ((mytext.value.search(re)) > -1)) {
return true;
}
else {
return false;
}
}



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